[Hypercoagulation caused by heparin-associated type II thrombocytopenia]

Area of Science:

• Cardiology
• Immunology
• Hematology

Background:

• Heparin-associated thrombocytopenia type II (HAT II) is a serious complication of heparin therapy, linked to arterial and venous thrombosis.
• Clinical suspicion of HAT II typically arises only in patients with critically low platelet counts (absolute thrombocytopenia).

Observation:

• A 44-year-old male experienced thromboembolic events, including reinfarction and brachial artery thrombosis, post-coronary angiography despite receiving fibrinolytic and unfractionated heparin therapy.
• This patient presented with normal platelet counts during the thromboembolic episodes, suggesting relative thrombocytopenia.
• Further investigations revealed an impaired fibrinolytic response, elevated antiphospholipid antibodies, and confirmed HAT II via HIPA and ELISA assays.

Findings:

• The case highlights that normal platelet counts do not exclude the possibility of HAT II.
• Relative thrombocytopenia, indicated by normal platelet counts during thrombotic events, can be a sign of HAT II.
• Elevated antiphospholipid antibodies and impaired fibrinolysis were noted in this patient.

Implications:

• Routine laboratory panel testing for HAT II is recommended for patients with thromboembolic episodes during heparin treatment, irrespective of absolute platelet count.
• This approach can aid in the early diagnosis and management of HAT II, potentially preventing further severe complications.
• The findings challenge the traditional reliance solely on absolute thrombocytopenia for suspecting HAT II.